Not sure if this even goes in here. I'm having some weird problems with creating a listen server. I need help testing a view things on a map I'm working on so i ask my friends. A couple days ago my friend connects perfectly fine to the server, but my other friend couldn't connect. Next day, that friend who couldn't connect connected fine. Today, i ask him to test again, and he couldn't connect, along with my other friend that i asked. Idk what the hell is going on. I do the same exact thing each time.

Load the map up, type in sv_lan 0, restart the map, give my IP to a friend, he types in connect MYIP, and joins and or doesn't join.

Didn't change anything, and for some reason sometimes they can connect, and sometimes they cant.

My ZoneAlarm Free Firewall would cause something like this when trying to host a listening server in Source engine games.

My game would be listed on the master server for a few moments, but then would soon disappear. Sometimes my friends could join, while other times they couldn't. It seemed to be random.

At first I thought my firewall was blocking port 27015 (which is required to be open while hosting HL2 listening servers), but the free version of ZoneAlarm doesn't allow you to open specific ports for programs so there as no way for me to test for certain. Even setting ZoneAlarm to Allow All Traffic would not fix my problem! :S

The ONLY way I could get my server to consistently show up was to completely shut down ZoneAlarm. I finally ended up switching to Comodo Firewall and all my problems are solved.

Moral of the story: try completely shutting down your firewall before you host and see if it works out better.